A typically known indoor unit for an air conditioner is provided in a ceiling. For example, Patent Document 1 shows a ceiling air conditioner (i.e., an indoor unit) including a casing, a decorative panel, and an inlet grille. The casing includes an indoor fan and an indoor heat exchanger inside, and is mounted in the ceiling. The decorative panel is attached to the lower end of the casing. The inlet grille is attached to an air inlet formed at a central portion of the decorative panel. This inlet grille includes a grille frame and a rectangular closed surface. The grille frame constitutes the outer edge of the grille. The closed surface constitutes the central portion of the grille. The closed surface projects beyond the grille frame to the inside of a room (i.e., downward). An inlet opening is formed between the grille frame and the closed surface.